First-principles study on the charge density wave of bulk and few-layer TiSe2
Y.H. Chan1*, C.M. Wei1, M.Y. Chou1,2,3
1IAMS, Academia Sinica, Taipei, Taiwan
2Department of Physics, National Taiwan University, Taipei, Taiwan
3School of Physics, Georgia Institute of Technology, Atlanta, United States of America
* presenting author:Yang-hao Chan,
The charge density wave (CDW) in TiSe2 has been discovered for more than three decades. Yet, the underlying mechanism of the formation of CDW in this material is still under debate. In this presentation we report the first-principles calculations with the screened hybrid functional HSE06 and the GW approximation. Our results agree with the experimental findings that both the normal and CDW phases are semiconductors with a 150 meV band gap. The band gap size in the normal phase suggests a pure excitonic mechanism is not favorable. We also observe a pressure-induced CDW-normal phase transition around 25 kilobars, which is comparable to earlier experimental results. The CDW phase in monolayer TiSe2 will also be discussed.

Keywords: Charge density wave, transition metal dichalcogenide